Common stock, without par value Common Stock [Member] Entity Tax Identification Number Entity Tax Identification Number Entity File Number Entity File Number Cover [Abstract] Cover [Abstract] Title of 12(b) Security Title of 12(b) Security Entities [Table] Entities [Table] Local Phone Number Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Soliciting Material Soliciting Material Entity Address, Address Line One Entity Address, Address Line One Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Entity Address, State or Province Entity Address, State or Province Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Written Communications Written Communications Entity Information [Line Items] Entity Information [Line Items] Trading Symbol Trading Symbol City Area Code City Area Code 2017 Series E 5.25% Junior Subordinated Debentures due 2077 Series E, 2017, 5.25% Junior Subordinated Debentures Due 2077 [Member] Series E, 2017, 5.25% Junior Subordinated Debentures Due 2077 [Member] Document Period End Date Document Period End Date 2020 Series G 4.375% Junior Subordinated Debentures due 2080 Series G, 2020, 4.375% Junior Subordinated Debentures Due 2080 [Member] Series G, 2020, 4.375% Junior Subordinated Debentures Due 2080 Amendment Flag Amendment Flag Pre-commencement Issuer Tender Offer Pre-commencement Issuer Tender Offer Entity Address, City or Town Entity Address, City or Town 2025 Series H 6.25% Junior Subordinated Debentures due 2085 Series H, 2025, 6.25% Junior Subordinated Debentures Due 2085 [Member] Series H, 2025, 6.25% Junior Subordinated Debentures Due 2085 Security Exchange Name Security Exchange Name Document Type Document Type Class of Stock [Axis] Class of Stock [Axis] Pre-commencement Tender Offer Pre-commencement Tender Offer Entity Central Index Key Entity Central Index Key 2021 Series E 4.375% Junior Subordinated Debentures due 2081 Series E, 2021, 4.375% Junior Subordinated Debentures Due 2081 [Member] Series E, 2021, 4.375% Junior Subordinated Debentures Due 2081 Entity Emerging Growth Company Entity Emerging Growth Company